I was just looking around the best way to write in urdu...online and it seems there are quite a few sites.
Best one is perhaps from google
Select Urdu from the drop down menu (At the moment it selects Hindi by default) and then write in roman english and it'll automatically translate it to urdu.
امید ہے کے یہ سب کے لئے کام کرے گا
Write on screen with the help of a virtual keyboard
Hope it helps someone